The Lovers Test

A man (M)
and a lady (L) who are very much in
love and devoted to one another, are separated by a river with no way
of getting across to the other side.

On L's side of the river, there is
a boatman (B) who is able to take
her over to the other side of the river but refuses to do so unless she
pays him a price of $20, twice his normal fare. L
has no money.

Another man (S) then tells L
that he will give her $20 if she sleeps with him. L
agrees to do so and on receiving the $20 pays B,
who takes her over to the other side of the river. She is reunited with
M and they are very happy together.

However, a friend of M's (F),
finds out what L did with S
and immediately tells M. On learning
the news, M goes to L
and ends things with her, stating that he wants nothing more to do with
her.

Your task is
to rank these five people, M, L,
B, S,
and F, from best person to worst person.